Total U.S. Military Personnel in Iraq Now at 825

WASHINGTON—The U.S. has increased surveillance efforts and has sent additional military advisers to Iraq to better aid national forces and understand the expanding extremist insurgency there, officials told Congress on Wednesday.

Since extremists seized control of Mosul in June, U.S. surveillance flights over Iraq have increased to nearly 50 a day, up from one flight a month, said Brett McGurk, the deputy assistant defense secretary...